Ester compounds, polymers, resist composition and patterning process

Abstract

A novel ester compound having an alkylcycloalkyl or alkylcycloalkenyl group as the protective group is provided as well as a polymer comprising units of the ester compound. The polymer is used as a base resin to formulate a resist composition having a higher sensitivity, resolution and etching resistance than conventional resist compositions.

What is claimed is:  
     
       1. A polymer comprising units of an ester compound of the following general formula (1a-1) or (1a-2):                    
       wherein R 1  is hydrogen, methyl or CH 2 C 2 R 4 ; R 2  is hydrogen, methyl or C 2 R 4 ; R 3  is a straight, branched or cyclic alkyl group of 1 to 8 carbon atoms or a substituted or unsubstituted aryl group of 6 to 20 carbon atoms; R 4  is a straight, branched or cyclic alkyl group of 1 to 15 carbon atoms; k is equal to 0 or 1, m is equal to 0 or 1, n is equal to 0, 1, 2 or 3, and 2m+n is equal to 2 or 3,  
       said polymer having a weight average molecular weight of 1,000 to 500,000.  
     
     
       2. The polymer of  claim 1  comprising recurring units of at least one of the following formulae (2a) to (10a):                  
                   
       wherein R 1  and R 2  are as defined above; R 5  is hydrogen or a monovalent hydrocarbon group of 1 to 15 carbon atoms containing a carboxyl or hydroxyl group; at least one of R 6  to R 9  represents a monovalent hydrocarbon group of 1 to 15 carbon atoms containing a carboxyl or hydroxyl group, and the remaining of R 6  to R 9  independently represent hydrogen or a straight, branched or cyclic alkyl group of 1 to 15 carbon atoms, or R 6  to R 9 , taken together, may form a ring with the proviso that at least one of R 6  to R 9  represents a divalent hydrocarbon group of 1 to 15 carbon atoms containing a carboxyl or hydroxyl group, and the remaining of R 6  to R 9  independently represent a straight, branched or cyclic alkylene group of 1 to 15 carbon atoms; R 10  is a monovalent hydrocarbon group of 3 to 15 carbon atoms containing a —CO 2 — partial structure; at least one of R 11  to R 14  represents a monovalent hydrocarbon group of 2 to 15 carbon atoms containing a —C 2 — partial structure, and the remaining of R 11  to R 14  independently represent hydrogen or a straight, branched or cyclic alkyl group of 1 to 15 carbon atoms, or R 11  to R 14 , taken together, may form a ring with the proviso that at least one of R 11  to R 14  represents a divalent hydrocarbon group of 1 to 15 carbon atoms containing a —CO 2 — partial structure, and the remaining of R 11  to R 14  independently represent a straight, branched or cyclic alkylene group of 1 to 15 carbon atoms; R 15  is a polycyclic hydrocarbon group of 7 to 15 carbon atoms or an alkyl group containing a polycyclic hydrocarbon group; R 16  is an acid labile group, and k is equal to 0 or 1.  
     
     
       3. A method for preparing a polymer comprising effecting radical polymerization, anionic polymerization or coordination polymerization between an ester compound of formula (1) and another compound having a carbon-to-carbon double bond. 
     
     
       4. A resist composition comprising the polymer of  claim 1 . 
     
     
       5. A resist composition comprising the polymer of  claim 1 , a photoacid generator, and an organic solvent. 
     
     
       6. A method for forming a pattern, comprising the steps of: 
       applying the resist composition of  claim 4  onto a substrate to form a coating,  
       heat treating the coating and exposing the coating to high energy radiation or electron radiation through a photo-mask,  
       optionally heat treating the exposed coating, and developing the coating with a developer.  
     
     
       7. A resist composition comprising the polymer of  claim 2 . 
     
     
       8. A resist composition comprising the polymer of  claim 2 , a photoacid generator, and an organic solvent. 
     
     
       9. A method for forming a pattern, comprising the steps of: 
       applying the resist composition of  claim 5  onto a substrate to form a coating,  
       heat treating the coating and exposing the coating to high energy radiation or electron radiation through a photo-mask,  
       optionally heat treating the exposed coating, and developing the coating with a developer.  
     
     
       10. A polymer according to  claim 1 , wherein R 3  is a methyl, ethyl, propyl, isopropyl, n-butyl, sec-butyl, tert-butyl, tert-amyl, n-pentyl, n-hexyl, cyclopentyl, cyclohexyl, cyclopentylmethyl, cyclopentylethyl, cyclohexylmethyl, cyclohexylethyl, phenyl, methylphenyl, naphthyl, anthryl, phenanthryl, or pyrenyl. 
     
     
       11. A polymer according to  claim 1 , wherein R 4  is methyl, ethyl, propyl, isopropyl, n-butyl, sec-butyl, tert-butyl, tert-amyl, n-pentyl, n-hexyl, cyclopentyl, cyclohexyl, ethylcyclopentyl, butylcyclopentyl, ethylcyclohexyl, butylcyclohexyl, adamantyl, ethyladamantyl, or butyladamantyl. 
     
     
       12. A polymer according to  claim 10 , wherein R 4  is methyl, ethyl, propyl, isopropyl, n-butyl, sec-butyl, tert-butyl, tert-amyl, n-pentyl, n-hexyl, cyclopentyl, cyclohexyl, ethylcyclopentyl, butylcyclopentyl, ethylcyclohexyl, butylcyclohexyl, adamantyl, ethyladamantyl, or butyladamantyl. 
     
     
       13. A polymer according to  claim 1 , wherein R 1  is H or CH 2 CO 2 CH 3 , R 2  is H or CO 2 CH 3 , and R 3  is methyl, ethyl, isopropyl, or n-butyl. 
     
     
       14. A polymer according to  claim 1 , wherein k is 0. 
     
     
       15. A polymer according to  claim 1 , wherein k is 1. 
     
     
       16. A polymer according to  claim 1 , wherein n is 2 or 3. 
     
     
       17. A polymer according to  claim 1 , wherein m is 0. 
     
     
       18. A polymer according to  claim 1 , wherein m is 1. 
     
     
       19. A polymer according to  claim 2 , wherein R 3  is ethyl, propyl, isopropyl, n-butyl, sec-butyl, tert-butyl, tert-amyl, n-pentyl, n-hexyl, cyclopentyl, cyclohexyl, cyclopentylmethyl, cyclopentylethyl, cyclohexylmethyl, cyclohexylethyl, phenyl, methylphenyl, naphthyl, anthryl, phenanthryl, or pyrenyl.